Police searching for missing mum Nicola Bulley are looking into all registered sex offenders in the area, a former officer has claimed.
Lancashire woman Nicola disappeared 18 days ago while walking her dog by the river in St Michael's on Wyre.
Her phone was found on a bench by the waterside and had recently connected to a work call. Her dog Willow was running loose.
Police launched an extensive search of the area with the Lancashire Police force still working on the theory that she fell in a river.
However, a body has not yet been found and the "open-minded" force was now probing other possibilities, including that the mortgage advisor was snatched or that she left on her own accord.
A former Scotland Yard veteran has now claimed that police are compiling a list of registered sex offenders in the region, which he explained was protocol.
Mick Neville, who was Metropolitan Police Detective Chief Inspector in charge of solving crimes with images, told MailOnline : "If there are any, their movements will be accounted for, as well as any similar cases being looked at again with this disappearance in mind.
"There will be an intelligence unit scouring all of this."
Police are said to be probing numerous lines of inquiry, including reports of two men acting suspiciously near Nicola's dog-walking route the day before she went missing,
A local witness told police about the two men the day before she vanished. He said they had been carrying fishing rods and appeared to be wearing hats or hoods, which hid their faces.
Meanwhile, a forensic expert has revealed he will begin his own search for Nicola Bulley in "deposition sites" near the river where she went missing.
Peter Faulding led a private underwater search team as he joined the search for the mum-of-two last week, but left the village after three days of scouring several miles of the river.
He has now launched his own "low-key" search and reportedly spoken to Ms Bulley's family about "deposition sites" - a term referring to a place where someone has been buried.
Nicola vanished while walking her springer spaniel Willow, shortly after dropping her daughters, aged six and nine, at school.
Yesterday, the mum's friends and family showed she has not been forgotten by leaving yellow ribbons with handwritten messages on a bridge close to where she disappeared.
Ribbons with messages including "We need you home Nicola", "praying for your safe return" and "I love you" have been tied to a footbridge over the River Wyre.
A large poster with a photograph of Ms Bulley has also been attached to the railings.
It comes as the search for Ms Bulley, 45, a mortgage adviser from Inskip, has entered the 18th day.
So far, the police search has been aided by specialists and divers from HM Coastguard, mountain rescue and Lancashire Fire and Rescue Service, with sniffer dogs, drones and police helicopters.
Ms Bulley's partner, Paul Ansell, said he wants to keep "all options open" about her disappearance, but his "gut instinct" tells him she is not in the river.
He described Ms Bulley as "fun", "loving", "the most loyal friend you could ever have" and an "exceptional mum" who "absolutely adores our girls".
